FIGS. 1A & B show a conventional prior art design for a metal-ceramic composite article comprising a metal shaft 10 joined by a conventional active metal braze composition to a ceramic ball 12. As shown, the metal shaft expands in diameter from the end which is joined to the ceramic ball 12 at an approximately 45.degree. angle. The maximum stress on the ceramic ball is exerted at points 14 and is calculated to be about 400 ksi by the finite element method of analysis. As a result of this relatively high stress the ceramic ball is subject to a very high incidence of cracking during or after cooldown from the elevated bonding temperature. Shafts attached to ceramic balls of this construction are used in various industrial devices such as check valves for pumps, safety valves for pipe lines, locater pins, and ball joints. Accordingly, it is important that they be reliable and have a long life in use. Thus, a shaftball design which reduces the stress on the ball and increases the reliability of the shaft/ball structure is needed.
U.S. Pat. Nos. 4,659,245, 4,747,722 and 4,679,960 are each directed to metal/ceramic articles which are designed to be of improved strength. None of the devices, however, are directed to a metal shaft attached to a ceramic ball and thus do not deal with the problem described with reference to FIGS. 1A & B herein.